1. Field of the Invention
The patent invention is related to electro-active polymer (EAP) or electromechanical polymer (EMP)1 actuators. In particular, the present invention is related to EAP- or EMP-based linear resonant actuators that provide a haptic response, suitable for use in handheld or mobile devices. 1 Electromechanical polymers (EMPs) refer to polymers that provide a mechanical response in response to a electrical stimulus and vice versa. EMPs are members of a broader class of polymers known as “electroactive (EAP) polymers,” which responses to electrical stimuli are not necessarily limited just to mechanical responses.
2. Discussion of the Related Art
Actuators that are light and miniaturized are highly desirable in many mobile applications. A class of actuators, known as linear resonant actuators (“LRAs”), use magnetic fields, electrical currents or both to control an actuator, so as to create a force that imparts motion to an attached mass. The mass may also be attached to a spring, which helps it return to a central quiescent position. Driving the mass in reciprocal motion about the central quiescent position causes a vibration. However, these actuators typically have a very narrow bandwidth, consume significant power and are limited in their applications because of their size. Resonance tuning of such actuators are also relatively difficult to provide.